One of the central problems relating to the practical implementation of such a holographic device is the considerable size of the data to be transmitted and displayed. A holographic image or hologram with a utilizable quality contains the items of information of several thousand perspectives of a scene at a given instant. If a sequence of images or video sequence is considered, this quantity of information must be multiplied by the refresh rate, thus culminating in bitrates well beyond the capacities of current networks.
The compression techniques customarily applied to conventional image sequences can be extended and generalized to encode holographic sequences; however, the very nature of holographic images prevents satisfactory results from being obtained since these techniques are generally based on block slicing and motion predictions; holographic images for their part take the form of diffraction patterns whose variations are almost entirely uncorrelated with the 3D scene that they represent.
A necessary expedient in the search for an efficient coding scheme is to identify the characteristics of the signal and the sources of the redundancies that may be found therein. This analysis leads to considering the local frequencies of the holographic patterns and consequently to favoring space/frequency decompositions, for which the decomposition functions used will have the best possible space/frequency location.
The use of a Gabor wavelet basis to decompose a holographic image for compression purposes is known from the document by Shortt, A. N, entitled “Compression of digital holograms of 3d objects using wavelets”, published in 2006 in the journal Optics Express, page 2625. Gabor wavelets constitute one of the most efficient procedures for extracting the relevant items of information from a holographic signal.
However, regardless of the efficiency of the wavelet scheme chosen, the size of the data does not make it possible to achieve compression rates that are satisfactory in regard to transmission and real-time display on existing networks.